WASHINGTON -- Wah Lim, a Chinese-born physicist, is at the center of the controversy over the possible transfer of sensitive satellite technology to China. But what's unclear is exactly how he got there.

Dr. Lim was working at Loral Space & Communications Ltd. in March 1996 when Beijing asked the company to review the cause of a fatal Chinese rocket explosion. China Aerospace Corp., the government company that launched the rocket, requested Dr. Lim to head the probe. Loral agreed, after firing the man who colleagues...